Field of the Invention
The present invention relates to mechanical feedback actuators, and more specifically, to a spring and damper configuration for a scissor mechanism for a mechanical feedback actuator.
Description of the Related Art
Mechanical feedback actuators can be used in applications where control feedback needs to be provided even if electrical power is lost. For example, liquid fuel rocket engines are often mounted to a space craft by gimbals, which enable the engines to pivot and provide steering control to the space craft. In the event that electrical power is lost onboard the space craft, it may be desirable for the liquid engines to center themselves so the aircraft flies straight ahead.
Mechanical feedback actuators can include a mechanical linkage between an actuator (e.g., a piston) and a controller for the actuator. When a first end of the mechanical linkage in contact with the actuator moves in response to the actuator moving, a second end of the mechanical linkage in contact with the controller can also move. The movement of the second end of the mechanical linkage can move a component of the controller to provide feedback for control of the actuator. For example, the controller may open a valve to send pressurized hydraulic fluid to displace an actuator by one inch. As the actuator reaches one inch of displacement, a corresponding motion of the second end of the mechanical linkage can exert a force that closes the valve, thereby stopping the actuator at one inch of displacement.
To provide mechanical feedback, the mechanical linkage needs to maintain contact with the actuator. Springs are often used to provide a force that pushes the mechanical linkage into contact with a feedback surface (e.g., a cam surface) of the actuator. However, springs can be susceptible to resonance. More specifically, strong vibrations can cause the springs to vibrate at a resonant frequency, which could result in the force being applied to the mechanical linkage dropping such that the mechanical linkage loses contact with the actuator. In such instances, the mechanical linkage could transmit an erroneous actuator position to the controller.